DESCRIPTION: (Applicant's Abstract) The goal of the laboratory is to better understand the molecular mechanisms of neural processing in the retina. It is known that the segregation of light stimuli into ON and OFF pathways is done at the level of the bipolar cells. Since it is thought that photoreceptor cells release glutamate as a neurotransmitter, the functional difference between ON and OFF bipolar cells is proposed to be the result of their expressing distinct glutamate receptors. Specifically this proposal aims to explore the relationship between the expression of different glutamate receptors and the diversity of bipolar cells in the mouse retina. 1.Glutmate receptors in OFF bipolar cells. The diversity and distribution of glutamate receptor subunits will be examined in OFF bipolar cells by in situ hybridization and immunonohistochemical analyses of horizontal and vertical retinal sections and dissociated retinal cells. Glutamate receptor subunit expression in electrophysiologically identified individual OFF bipolar cells will be determined using the PCR technique. 2.Glutamate receptors in ON bipolar cells. The APB-type glutamate receptor, which is thought to mediate the sign inversion in ON bipolar cells, will be cloned. Antibodies will be raised against fragments of the APB receptor expressed in bacteria. The diversity and distribution of glutamate receptors will be examined in ON bipolar cells by in situ hybridization and immunohistochemical analyses of horizontal and vertical retinal sections and dissociated retinal cells. Glutamate receptor expression in electrophysiologically identified individual ON bipolar cells will be analyzed using the PCR technique. 3.Glutamate receptors during development. Studies have shown an early exrpession of neurotransmitter receptors in the developing brain, suggesting some role in the establishment of neural circuitry. The regulation of glutamate receptor expression in relation to the differentiation of bipolar cells will be analyzed using in situ hybridization and immunohistochemistry. The research proposed here will provide the basis with which to analyze the expression of glutamte receptors in mice with retinal degenerations and to assess the effects of receptor alterations during development and in the adult retina using transgenic mice.